The present invention relates to a milling cutter for carrying out milling work on work such as a crank shaft.
Generally, work such as crank shaft of an engine is milled by using a cutter for performing the milling working. However, as in FIG. 1, showing a milling state of a work 100, when an outer periphery of a pin 101 of the work 100, journal thrusts 102 positioned at both ends of the pin 101 and side surfaces 104 of counterweights 103 are worked, the following work method has been adopted in the prior art.
That is, as shown in FIG. 2A, when grooving work is carried out on both ends of the pin 101, the outer periphery of the pin 101, the journal thrusts 102 and the side surfaces 104 of the counterweights 103 are first roughly worked at the same time (cutting a margin shown by reference numeral 105), and then grooving work is performed together with finish cutting work on the outer periphery of the pin 101 and the journal thrusts 102 (cutting a margin shown by reference numeral 106). Thereafter, grinding finish work is effected on the outer periphery of the pin 101 (cutting a margin shown by reference numeral 107). In such work, in the technology disclosed in the Japanese Patent Laid-open Publication No. HEI 5-253729, one of tips for carrying out side surface work is used as a flat drag set to a maximally deviated state for improving the surface roughness of the journal thrust 102.
Furthermore, as shown in FIG. 2B, in a case where grooving work is not effected on both the ends of the pin 101, the outer periphery of the pin 101, the journal thrusts 102 and the side surfaces 104 of the counterweights 103 are first roughly worked, and then finish work is effected on the outer periphery of the pin 101 and the journal thrusts 102 through lathe turning or milling work as an independent process. Thereafter, cutting finish work is effected on the outer periphery of the pin 101 or, as shown in FIG. 2C, rough work is effected, and then the cutting finish work is effected simultaneously on the outer periphery of the pin 101 and the journal thrusts 102.
In both the methods mentioned above, the outer periphery of the pin 101 and the journal thrusts 102 are subjected to the finish work after the rough work on the outer periphery of the pin 101, the journal thrusts 102 and the side surfaces 104 of the counterweights 103. In these work methods in which the grinding work is not effected as shown in FIGS. 2B and 2C, substantially the same number of working processes as those in the work method, including the grooving work shown in FIG. 2A, are required, so that all of these working methods require a lot of work time, resulting in less workability and productivity, and thus providing a problem.